Calcium is the chemical element present in chalk, limestone, gypsum, and calcite. The adjectives calciferous and calcareous refer to minerals that contain calcium or lime. A calcicole (Latin colere, inhabit) is a plant that needs a soil containing lime. Calciferol (from calciferous plus -ol) is the formal name for Vitamin D, essential for metabolizing calcium in the body; conversely, calcitonin is a hormone that reduces calcium levels in the blood. The Latin word for a small stone, calculus, is used in medicine for a stone in the kidney or gall bladder; small stones were used as markers on Roman counting tables and the English mathematical terms calculate and calculus derive from this.